Adriamycin and cytoxan are two chemotherepeutic agents widely used in the treatment of malignant tumors. We prospectively followed 25 patients by serial radionuclide angiography to determine the incidence and severity of the cardiac damage caused by these agents. Only patients free of preexisting heart disease with normal resting LV ejection fractions were studied. After treatment with adriamycin and cytoxan only 4 patients developed clinical evidence for heart failure. By radionuclide testing, however, 24 patients showed some evidence for cardiac damage. Twelve patients developed subnormal resting LV ejection fractions. These data appear to indicate that in the absence of underlying heart disease it is uncommon for adriamycin or cytoxan to cause clinically significant LV dysfunction. Furthermore, serial radiononuclide angiography appears to be a sensitive method for following patients receiving these agents.